JP5963721B2 - Light guide, illumination device, image reading device, and image forming device - Google Patents

Description

The present invention relates to a light guide used for illumination, an illumination device including the light guide, an image reading device including the illumination device, and an image forming apparatus .

  An example of this type of lighting device is disclosed in Patent Document 1. In this Patent Document 1, a light emitting surface is formed on the side surface along the longitudinal direction of the rod-shaped light guide, and a saw blade-like light reflecting surface is formed on the other side surface along the longitudinal direction of the light guide. The light exiting surface and the light reflecting surface are opposed to each other, the light from the light source is incident on the longitudinal end surface of the light guide to propagate inside the light guide, and the light is directly emitted from the light exit surface of the light guide. Further, the light is reflected by the light reflecting surface and emitted from the light emitting surface, and the surface of the original is illuminated by the emitted light. Further, the distribution of the amount of light emitted from the light exit surface is appropriately set by adjusting the inclination angle distribution of each of the inclined surfaces forming the saw-tooth shaped light reflecting surface.

  Moreover, in patent document 2, the light-projection surface which has a semicircular cross-sectional shape is formed in the side surface along the longitudinal direction of a rod-shaped light guide, and the light-scattering surface is formed in the other side surface along the longitudinal direction of a light guide. Then, the light emitting surface and the light scattering surface are opposed to each other, and a plurality of light sources are disposed on the end surface of the light guide so that the light of each light source is incident on the end surface of the light guide. The light is directly emitted from the light emitting surface, reflected by the light scattering surface and emitted from the light emitting surface, and the emitted light illuminates the document surface. In addition, by adjusting the arrangement position of each light source, the emitted light quantity distribution emitted from the light emitting surface is appropriately set.

JP 2000-89030 A JP 2011-188080 A

  However, as in Patent Document 1, it is not easy to adjust the inclination angle distribution of each inclined surface forming the saw-tooth-like light reflecting surface, and no matter how the inclination angle distribution of each inclined surface is adjusted. The emitted light quantity distribution did not change smoothly, and a step was generated in the change in the emitted light quantity distribution.

  Moreover, when providing several light sources in the end surface of a light guide like patent document 2, the number of parts and cost increased. Further, in order to set the distribution of the quantity of emitted light emitted from the light exit surface more accurately, it is necessary to increase the number of each light source, and the number of parts and the cost have increased further.

Accordingly, the present invention has been made in view of the above-described conventional problems, and a light guide capable of smoothly changing the distribution of emitted light quantity and causing no increase in the number of parts and cost, and the light guide. It is an object of the present invention to provide an illuminating device including the illuminating device, an image reading device including the illuminating device, and an image forming apparatus .

In order to solve the above-described problems, a light guide body according to the present invention includes a long main body having translucency, a light incident surface formed at a longitudinal end of the main body, and a longitudinal direction of the main body. A light emitting surface formed on the side surface along the side, and an emission light amount adjusting unit formed on the other side surface along the longitudinal direction of the main body and facing the light emitting surface, and the light incident on the light incident surface A light guide that guides light inside the body, reflects off the light output adjustment unit, and emits light from the light exit surface, and the light output adjustment unit has a width in a direction perpendicular to the longitudinal direction, It changes depending on the position in the longitudinal direction, is constant in the central region in the longitudinal direction, and gradually becomes narrower as it approaches the end in the longitudinal direction in both side regions of the central region, and is orthogonal to the longitudinal direction. In the direction, the width of the light exit surface and the width of the emitted light amount adjustment unit , Characterized in that to match the width of the body.

  In such a light guide of the present invention, the width of the emitted light amount adjusting unit in the direction orthogonal to the longitudinal direction of the main body is changed depending on the position of the light guide in the longitudinal direction. Here, the light is incident on the light incident surface of the main body, is guided inside the main body, is reflected by the emitted light amount adjusting unit, and is emitted from the light emitting surface. Therefore, the light is emitted as the width of the emitted light amount adjusting unit becomes wider. The amount of reflected light at the light amount adjustment unit increases, the amount of light emitted from the light output surface increases, and conversely, the amount of reflected light at the output light amount adjustment unit decreases as the width of the output light amount adjustment unit becomes narrower. The amount of light emitted from the beam decreases. For this reason, if the width | variety of an emitted light quantity adjustment part is changed with the position of the longitudinal direction of a light guide, the emitted light quantity reflected by the emitted light quantity adjustment part and radiate | emitted from a light-projection surface will change with the position of a longitudinal direction. Therefore, the emitted light quantity distribution in the longitudinal direction can be appropriately set by changing the width of the emitted light quantity adjusting unit according to the position in the longitudinal direction of the light guide.

On the other hand, the illumination device of the present invention includes the light guide of the present invention and a light source that emits light to the light incident surface of the light guide.

The image reading device of the present invention includes the above-described illumination device of the present invention and a reading unit that reads the irradiated object illuminated by the light emitted from the light emitting surface of the light guide of the illumination device. ing.

An image forming apparatus according to the present invention includes the image reading device according to the present invention and a printing unit that prints an image of the irradiated object read by the image reading device on a recording sheet.

  On the other hand, the illumination device of the present invention includes the light guide of the present invention and a light source that emits light to the light incident surface of the light guide.

  The image reading device of the present invention includes the above-described illumination device of the present invention and a reading unit that reads the irradiated object illuminated by the light emitted from the light emitting surface of the light guide of the illumination device. ing.

  Such an illuminating device and an image reading device also have the same effects as the light guide of the present invention.

  In the present invention, since the width of the emitted light amount adjusting unit in the direction orthogonal to the longitudinal direction of the main body is changed depending on the position in the longitudinal direction of the light guide, it is reflected by the emitted light amount adjusting unit and emitted from the light emitting surface. The amount of emitted light varies depending on the position in the longitudinal direction. Therefore, the emitted light quantity distribution in the longitudinal direction can be appropriately set by changing the width of the emitted light quantity adjusting unit according to the position in the longitudinal direction of the light guide.

1 is a cross-sectional view illustrating an image forming apparatus including a first embodiment of an image reading apparatus of the present invention. FIG. 2 is a cross-sectional view illustrating the image reading device and the document conveying device of FIG. 1. It is sectional drawing which expands and shows the scanning unit in an image reading apparatus. It is a perspective view which shows the scanning unit of FIG. It is a perspective view which expands and shows the edge part of a scanning unit. In a scanning unit, it is a perspective view which expands and shows the state which removed the heat sink and exposed the LED board. In a scanning unit, it is a perspective view which expands and shows the state which removed the LED board and the heat sink and exposed the edge part of the lid-shaped holding member. It is a perspective view which extracts each light guide and each LED of the illuminating device in a scanning unit, and sees it from upper direction. It is a perspective view which shows each light guide and each LED of the illuminating device of FIG. 8 seeing from the downward direction. It is a perspective view which expands and shows the light guide of an illuminating device. (A) is a plan view showing the light guide, (b) is a side view showing the light guide, (c) is a graph showing the emitted light quantity distribution from the light exit surface of the light guide, (D) is a graph showing the transmitted light amount distribution of the imaging lens, and (e) is a graph showing the received light amount distribution received by the light receiving surface of the CCD. (A) is a top view which shows the light guide of a comparative example, (b) is a side view which shows the light guide of a comparative example, (c) is from the light-projection surface of the light guide of a comparative example. It is a graph which shows emitted light amount distribution, (d) is a graph which shows the transmitted light amount distribution of an imaging lens, (e) is a graph which shows received light amount distribution received by the light-receiving surface of CCD. (A) is a top view which shows the light guide in 2nd Embodiment, (b) is a side view which shows the light guide in 2nd Embodiment, (c) is the light guide in 2nd Embodiment. 2 is a graph showing the distribution of the amount of light emitted from the light exit surface of FIG. 2, (d) is a graph showing the distribution of the transmitted light amount of the imaging lens, and (e) is a graph showing the distribution of the amount of light received by the light receiving surface of the CCD. It is.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing an image forming apparatus provided with a first embodiment of an image reading apparatus of the present invention. The image forming apparatus 1 has a copying function of reading a document and printing it on a recording sheet, and includes an image reading device 2, a document conveying device 3, a printing unit 4, a paper feed cassette 5, and the like.

  The image data handled in the image forming apparatus 1 corresponds to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This corresponds to the monochrome image used. For this reason, the printing unit 4 is provided with four developing devices 12, photosensitive drums 13, drum cleaning devices 14, and chargers 15 in order to form four types of toner images corresponding to the respective colors. Four image stations Pa, Pb, Pc, and Pd are configured in association with black, cyan, magenta, and yellow.

  In each of the image stations Pa, Pb, Pc, and Pd, after the residual toner on the surface of the photosensitive drum 13 is removed and collected by the drum cleaning device 14, the surface of the photosensitive drum 13 is set to a predetermined potential by the charger 15. It is charged uniformly, the surface of the photosensitive drum 13 is exposed by the optical scanning device 11, an electrostatic latent image is formed on the surface, and the electrostatic latent image on the surface of the photosensitive drum 13 is developed by the developing device 12, A toner image is formed on the surface of the photosensitive drum 13. As a result, a toner image of each color is formed on the surface of each photosensitive drum 13.

  Subsequently, while the intermediate transfer belt 21 is moved in the direction of the arrow C, the residual toner on the intermediate transfer belt 21 is removed and collected by the belt cleaning device 25, and then each color toner image is transferred onto the surface of each photosensitive drum 13. The toner images are sequentially transferred onto the belt 21 and overlapped to form a color toner image on the intermediate transfer belt 21.

  A nip area is formed between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26, and the recording sheet conveyed through the sheet conveyance path R1 is sandwiched and conveyed in the nip area. The color toner image on the surface of the intermediate transfer belt 21 is transferred onto a recording sheet. Then, the recording paper is sandwiched between the heating roller 31 and the pressure roller 32 of the fixing device 17 and heated and pressed to fix the color toner image on the recording paper.

  On the other hand, the recording sheet is pulled out from the sheet feeding cassette 5 by the pickup roller 33 and conveyed through the sheet conveying path R 1, via the secondary transfer device 26 and the fixing device 17, and discharged from the sheet discharge roller 36. To 39. In this paper conveyance path R1, after the recording paper is temporarily stopped and the leading edges of the recording paper are aligned, recording is performed in accordance with the transfer timing of the color toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 26a. A registration roller 34 for starting the conveyance of the paper, each conveyance roller 35 for urging the conveyance of the recording paper, a paper discharge roller 36, and the like are arranged.

  When printing not only on the front side of the recording paper but also on the back side, the recording paper is conveyed in the reverse direction from the paper discharge roller 36 to the reverse path Rr, so that the front and back sides of the recording paper are reversed and the recording paper is registered. The image is guided again to the roller 34, and the image is recorded and fixed on the back surface of the recording paper, similarly to the front surface of the recording paper, and the recording paper is carried out to the paper discharge tray 39.

  Next, the image reading device 2 of the first embodiment will be described. FIG. 2 is a cross-sectional view showing the image reading device 2 and the document conveying device 3.

  In FIG. 2, the document conveying device 3 is pivotally supported on one side of the lower image reading device 2 by a hinge (not shown) and opened and closed by moving the front side up and down. When the document conveying device 3 is opened, the document placing glass 41 of the image reading device 2 is opened.

  The image reading apparatus 2 includes a document placing glass 41, a document reading glass 42, a scanning unit 43, a moving unit 44, and the like. The moving unit 44 includes a guide shaft 48 that guides the scanning unit 43 in the sub-scanning direction Y, and a drive unit (not shown) that moves and positions the scanning unit 43 in the sub-scanning direction Y.

  The scanning unit 43 includes an illumination device 45, an imaging lens 46, a CCD (Charge Coupled Device) 47, first to fourth reflecting mirrors 51 to 54, and the like. 42, the original (illuminated body) placed on the original placing glass 41 is read (first reading mode), or the original conveyed on the original reading glass 42 (irradiated) Body) (second reading mode).

  In the first reading mode, the scanning unit 43 is moved below the document placement glass 41 by the moving unit 44, the document transport device 3 is opened, the document is placed on the document placement glass 41, and the document transport device 3. Close. Then, while the scanning unit 43 is moved by the moving unit 44 in the sub-scanning direction Y by a distance corresponding to the document size at a constant speed, the document on the document placement glass 41 is illuminated by the illumination device 45, and the reflected light is reflected by The light is sequentially reflected by the first to fourth reflecting mirrors 51 to 54 and guided to the imaging lens 46. The imaging lens 46 condenses the reflected light from the document on the CCD 47 and forms an image on the surface of the document on the CCD 47. The CCD 47 repeatedly scans the image on the document surface in the main scanning direction X and reads the image on the document surface.

  In the second reading mode, the scanning unit 43 is moved and positioned below the original reading glass 42 by the moving unit 44, and the original is pulled out from the original placing tray 56 by the original conveying device 3, and the sub scanning is performed on the original reading glass 42. It is conveyed in the scanning direction Y and discharged to the document discharge tray 57. When the original passes over the original reading glass 42, the illumination device 45 of the scanning unit 43 illuminates the original surface through the original reading glass 42, and the reflected light from the original surface is reflected by the first to fourth of the scanning unit 43. The light is sequentially reflected by the reflecting mirrors 51 to 54 and guided to the imaging lens 46, and the reflected light from the document surface is condensed on the CCD 47 by the imaging lens 46 to form an image on the document surface on the CCD 47. Thus, the image on the document surface is repeatedly scanned in the main scanning direction X to read the image on the document surface.

  Next, the illumination device 45 of the scanning unit 43 will be described in detail. FIG. 3 is an enlarged sectional view showing the scanning unit 43. 4 is a perspective view showing the scanning unit 43, and FIG. 5 is an enlarged perspective view showing an end portion of the scanning unit 43. As shown in FIG. As shown in FIGS. 3 to 5, the scanning unit 43 includes a housing 61 having an opening on the upper side, a lid-like holding member 62 provided in the upper opening of the housing 61, and a lid-like holding member. And a CCD substrate 63 provided on a side wall along the longitudinal direction (main scanning direction X) of the housing 61.

  An imaging lens 46 and first to fourth reflection mirrors 51 to 54 are provided inside the housing 61. The lid-shaped holding member 62 substantially covers the upper opening of the housing 61 and holds the lighting device 45. Furthermore, the CCD 47 is mounted on the CCD substrate 63, and the light receiving surface of the CCD 47 faces the inside of the housing 61 through a slit (not shown) formed on the side wall of the housing 61.

  The lid-shaped holding member 62 is formed with two fitting grooves 62a that are long in the main scanning direction X and slits St between the fitting grooves 62a. The illuminating device 45 has each light guide 71 fitted in each fitting groove 62a, and each side surface along the main scanning direction X of each light guide 71 is defined as each light emitting surface 71a. Light is emitted from the light emission surface 71a. The light emitted from the light exit surface 71a of each light guide 71 is transmitted through the document placement glass 41 or the document reading glass 42, is irradiated on the document, and is reflected by the document. The light reflected by the document passes through the document placement glass 41 or the document reading glass 42 and is guided to the inside of the housing 61 through the slit St of the lid-shaped holding member 62, and the first to fourth reflection mirrors 51. Are sequentially reflected by .about.54 and enter the CCD 47 through the imaging lens 46. FIG.

  In addition to the two light guides 71, the illumination device 45 includes four LEDs (not shown) disposed at both ends of each light guide 71, and two LEDs each mounted with two LEDs. The LED board 64 and the two heat sinks 65 provided so as to overlap the outside of each LED board 64 are provided.

  FIG. 6 is an enlarged perspective view showing a state in which the heat sink 65 is removed and the LED board 64 is exposed, and FIG. 7 is a perspective view of the lid-shaped holding member 62 with the LED board 64 and the heat sink 65 removed. It is a perspective view which expands and shows the state which exposed the edge part. As shown in FIGS. 6 and 7, the lid-shaped holding member 62 has the shielding portions 62 b and 62 c covering the range except the slit St in the upper opening of the housing 61, and both end portions of the shielding portions 62 b and 62 c. It has each connection part 62d to connect. Respective fitting grooves 62a (shown in FIG. 3) are formed in the respective shielding portions 62b and 62c, and the respective light guides 71 are fitted into the respective fitting grooves 62a.

  The connecting portion 62d of the lid-like holding member 62 is formed with two opening holes 62e that communicate with the respective fitting grooves 62a. The light guide 71 has a quadrangular prism shape, and both end faces thereof are light incident surfaces 71b, and the light incident surfaces 71b of the two light guides 71 are disposed in the respective opening holes 62e. . Further, the light emitting surface 71a of the light guide 71 facing the document placing glass 41 or the document reading glass 42 is exposed, and the other three side surfaces other than the light emitting surface 71a are arranged inside the fitting groove 62a. Yes.

  Further, the connecting portion 62d of the lid-like holding member 62 is formed with a screw hole 62f located at the center of the connecting portion 62d and two pins 62g and 62h located on both sides of the screw hole 62f. The LED board 64 is formed with one mounting hole 64 a and two positioning holes 64 b and 64 c located on both sides of the mounting hole 64 a, and two LEDs (light sources) 72 on one side of the LED board 64. Has been implemented. Instead of the LED, other types of semiconductor elements, light bulbs, and the like may be applied. The heat radiating plate 65 is made of metal and includes a main plate 65a and two side plates 65b bent at both ends of the main plate 65a. The main plate 65a is formed with one mounting hole 65c and two positioning holes 65d and 65e located on both sides of the mounting hole 65c, and a notch 65f is formed on the upper side of each side plate 65b. Has been.

  Here, when the pins 62g and 62h projecting from the connecting portion 62d of the lid-like holding member 62 are inserted into the positioning holes 64b and 64c of the LED substrate 64, and the LED substrate 64 is superimposed on the connecting portion 62d, The LED board 64 is positioned with respect to the connecting part 62d, and the mounting hole 64a of the LED board 64 overlaps the screw hole 62f of the connecting part 62d. Further, each LED 72 on the LED substrate 64 is disposed in each opening hole 62e of the connecting portion 62d, and the light emitting surface of each LED 72 faces the light incident surface 71b of each light guide 71 inside the each opening hole 62e. The light emitted from the light emitting surface of each LED 72 can enter the light incident surface 71 b of each light guide 71.

  Further, the pins 62g and 62h projecting from the connecting portion 62d of the lid-like holding member 62 are inserted into the two positioning holes 65d and 65e of the main plate 65a of the heat sink 65, and the main plate 65a of the heat sink 65 is connected to the LED. When superposed on the substrate 64, the main plate 65a of the heat radiating plate 65 is positioned with respect to the connecting portion 62d and the LED substrate 64, and the mounting hole 65c of the main plate 65a of the heat radiating plate 65 is connected to the mounting hole 64a of the LED substrate 64 and the connecting portion 62d. It overlaps with the screw hole 62f. In this state, the screw 73 is passed through the mounting hole 65c of the main plate 65a of the heat radiating plate 65 and the mounting hole 64a of the LED substrate 64 and screwed into the screw hole 62f of the connecting portion 62d to be fastened. Is fixed to the connecting portion 62d. The heat radiating plate 65 and the LED substrate 64 are fixed to both of the connecting portions 62 d at both ends of the lid-like holding member 62, and the respective LEDs 72 are arranged to face the light incident surfaces 71 b at both ends of each light guide 71. .

  FIG. 8 is a perspective view showing the light guides 71 and the LEDs 72 of the illumination device 45 extracted from the top, and FIG. 9 is a perspective view showing them from the bottom. As shown in FIGS. 8 and 9, in the illuminating device 45, the light guides 81 are arranged on both sides of the slit St extending in the main scanning direction X, and the LEDs 72 are provided on the light incident surfaces 71 b at both ends of the light guides 81. Is arranged.

  The light guide body 71 is a light-transmitting quadrangular prism and is formed of a long light-transmitting main body. Light-transmitting surfaces 71b are formed at both ends in the longitudinal direction Q of the light-transmitting main body, respectively. A light emitting surface 71a is formed on one side surface along the longitudinal direction Q of the main body, and an emitted light amount adjusting unit 71e facing the light emitting surface 71a is formed on the other side surface along the longitudinal direction Q of the translucent main body. A light reflecting surface 71d is formed in a region of the side surface where the outgoing light amount adjusting portion 71e is not formed. Such a light guide 71 is formed by molding an acrylic resin with a mold.

  As shown in an enlarged view in FIG. 10, the light reflecting surface 71d is a flat surface. In addition, the emitted light amount adjusting unit 71e has a saw blade-like vertical cross-sectional shape, and has a large number of inclined surfaces 71f that form a saw-blade vertical cross-sectional shape.

  In the illuminating device 45 having such a configuration, the LEDs 72 are opposed to the light incident surfaces 71 b at both ends of the light guide 71, so that the light emitted from each LED 72 is incident on the light guide 71. The light is incident on the surface 71b, guided inside the light guide 71, and directly emitted from the light emitting surface 71a, or reflected by the light reflecting surface 71d or the emitted light amount adjusting unit 71e and emitted from the light emitting surface 71a. . At this time, the sawtooth-shaped emission light amount adjustment unit 71e is diffused and emitted from the light emission surface 71a after being guided inside the light guide 71 and incident on the emission light amount adjustment unit 71e.

  The light emission surface 71a of each light guide 71 is directed to the same location of the document via the document placement glass 41 or the document reading glass 42, and is emitted from the light emission surface 71a of each light guide 71. Is incident on the same portion of the document, the portion of the document is illuminated, and the light reflected at that portion of the document is guided to the inside of the housing 61 through the slit St.

  By the way, the amount of light emitted from the light incident surface 71b of the light guide 71 is not uniform in the longitudinal direction Q of the light guide 71, but near both ends near the LEDs 72 of the light guide 71 rather than near the center of the light guide 71. It tends to increase. In addition, the peripheral light amount is reduced by the cosine fourth law of the imaging lens 46 of the scanning unit 43. Accordingly, although the deviation of the emitted light amount and the peripheral light amount tend to cancel each other, it still does not cancel well, and the received light amount distribution received by the light receiving surface of the CCD 47 is shifted. For this reason, it is desirable that the distribution of the amount of light emitted from the light incident surface 71 b of the light guide 71 is adjusted to make the distribution of the amount of received light received by the light receiving surface of the CCD 47 uniform.

  However, in order to adjust the emitted light amount distribution from each light guide 71 as in the prior art, the inclination angle distribution of each inclined surface 71f that forms the sawtooth vertical cross-sectional shape of the emitted light amount adjusting unit 71e is adjusted. It is not easy, and no matter how the inclination angle distribution is adjusted, a step is generated in the change in the emitted light amount distribution. Alternatively, when the area of the light incident surfaces 71b at both ends of the light guide 71 is widened to increase the number of LEDs 72 and the emitted light quantity distribution is adjusted by setting the arrangement positions of the LEDs 72, the number of parts and the cost are reduced. Increase.

  Therefore, in the first embodiment, as shown in FIG. 11A, the width F of the emitted light amount adjusting unit 71e in the direction orthogonal to the longitudinal direction Q of the light guide 71 is set to be approximately equal to the light at both ends of the light guide 71. As it gets closer to the incident surface 71b, it gradually becomes narrower. Specifically, in the central region 71g of the light guide 71, the width F of the emitted light amount adjusting unit 71e in the direction orthogonal to the longitudinal direction Q of the light guide 71 is constant, and in the both side regions 71h of the central region 71g, the emitted light amount. The width F of the adjusting portion 71e is gradually narrowed as it approaches the light incident surfaces 71b at both ends of the light guide 71.

  Further, as shown in FIG. 11B, the pitch, height, and width (of the light guide 71) of each inclined surface 71f (shown in FIG. 10) forming the sawtooth-shaped vertical section of the outgoing light amount adjusting unit 71e. The width of the inclined surface 71f in the longitudinal direction Q) is set constant.

  FIG. 11C shows an emitted light amount distribution emitted from the light emitting surface 71a of the light guide 71 to the document. In this outgoing light quantity distribution, the light quantity increases as it approaches the both ends of the light guide 71, and the light quantity tends to decrease as it approaches the center of the light guide 71. This is because the light of each LED 72 is made incident on the light incident surfaces 71 b at both ends of the light guide 71, so that the amount of light inside the light guide 71 increases as it approaches the both ends of the light guide 71.

  However, as shown in FIG. 11A, in the central region 71g of the light guide 71, the width F of the emitted light amount adjusting unit 71e is kept constant, so that the reflected light amount at the emitted light amount adjusting unit 71e is reduced. The amount of light emitted from the light exit surface 71a is also maintained without decreasing. In addition, in both side regions 71h of the light guide 71, the width F of the emitted light amount adjusting unit 71e is gradually narrowed toward the light incident surfaces 71b at both ends of the light guide 71. The closer to the light incident surface 71b, the smaller the amount of light reflected by the emitted light amount adjusting unit 71e, and the smaller the amount of light emitted from the light emitting surface 71a. For this reason, in the emitted light quantity distribution shown in FIG. 11C, the degree of decrease in the emitted light quantity near the center of the light guide 71 is corrected by Δs with respect to the emitted light quantity near both ends of the light guide 71. That is, the amount of emitted light near the center of the light guide 71 is raised by Δs.

  The emitted light amount distribution of the light guide 71 is equivalent to the irradiated light amount distribution on the document surface. Moreover, in 1st Embodiment, although the width | variety of the light reflection surface 71d is changing with the position of the longitudinal direction Q of the light guide 71, the light quantity reflected by this light reflection surface 71d is shown in FIG.11 (c). There is no significant effect on the emitted light quantity distribution.

  FIG. 11D shows a transmitted light amount distribution (peripheral dimming characteristics of the imaging lens 46) that passes through the imaging lens 46 and enters the light receiving surface of the CCD 47. In the transmitted light amount distribution shown in FIG. 11D, the light amount decreases as it approaches the both ends of the imaging lens 46 according to the cosine fourth law of the imaging lens 46, and the light amount increases as it approaches the center of the imaging lens 46. Yes.

  Here, in the emitted light amount distribution from the light emitting surface 71 a of the light guide 71 shown in FIG. 11C, the light amount increases as it approaches the light incident surfaces 71 b at both ends of the light guide 71. The light quantity tends to decrease as it approaches the center, and in the transmitted light quantity distribution transmitted through the imaging lens 46 shown in FIG. 11D, the light quantity decreases as it approaches the both ends of the imaging lens 46. The amount of light tends to increase as it approaches the center of the screen. For this reason, the deviation of the emitted light amount distribution shown in FIG. 11C and the deviation of the transmitted light amount distribution shown in FIG. 11D tend to cancel each other. In addition, the width F of the outgoing light amount adjusting unit 71e is widened in the vicinity of the center of the light guide 71 and gradually becomes narrower as it approaches the light incident surfaces 71b at both ends of the light guide 71, and near the center of the light guide 71. 11 is corrected by Δs, the deviation of the emission light quantity distribution in FIG. 11C and the deviation of the transmitted light quantity distribution in FIG. As a result, the received light amount distribution received by the light receiving surface of the CCD 47 is uniform as shown in FIG.

  Further, as apparent from FIG. 11C, the emitted light quantity distribution changes smoothly and does not change so as to produce a step, so that the peripheral light quantity caused by the cosine fourth law of the imaging lens 46 is reduced. It can compensate well.

  Next, as a comparative example, a light guide 71A in which the width F of the emitted light amount adjusting unit 71e is constant will be described.

  In the comparative example, as shown in FIG. 12A, the width F of the emitted light amount adjusting unit 71e in the direction orthogonal to the longitudinal direction Q of the light guide 71A is made to coincide with the constant width of the light guide 71A. For this reason, the light guide 71A does not have a surface corresponding to the light reflecting surface 71d of the light guide 71 in FIG.

  In addition, as shown in FIG. 12B, the pitch, height, and width of each inclined surface 71f forming the sawtooth-shaped vertical section of the outgoing light amount adjusting unit 71e (the inclined surface in the longitudinal direction Q of the light guide 71). The width of 71f is set constant.

  In this case, the distribution of the amount of emitted light emitted from the light emitting surface 71a to the original is as shown in FIG. Since the light guide 71A of the comparative example has a constant width F of the emitted light quantity adjusting unit 71e, even if the emitted light quantity in the vicinity of the center of the light guide 71 is maintained without decreasing, the vicinity of both ends of the light guide 71 Thus, the amount of emitted light near the center of the light guide 71A is reduced by Δs as compared with the distribution of the amount of emitted light of the light guide 71 shown in FIG. 11C. The reduction in the amount of emitted light near the center is not reduced.

  For this reason, the deviation of the emitted light amount distribution of the light guide 71A shown in FIG. 12C and the deviation of the transmitted light amount distribution of the imaging lens 46 shown in FIG. As shown in (e), the distribution of the amount of light received by the light receiving surface of the CCD 47 is not uniform, but is greatly reduced near the center of the light receiving surface. Therefore, the decrease in the amount of peripheral light caused by the cosine fourth law of the imaging lens 46 is not compensated.

  Next, the image reading apparatus 2 according to the second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in that a light guide 71B as shown in FIGS. 13A and 13B is used instead of the light guide 71 of the illumination device 45. .

  In the second embodiment, as shown in FIG. 13 (a), the width of the light guide 71B in the direction orthogonal to the longitudinal direction Q of the light guide 71B is approximately equal to the light incident surfaces 71b at both ends of the light guide 71B. The width of the light emitting surface 71a of the light guide 71B and the width F of the emitted light amount adjusting unit 71e are made to coincide with the width of the light guide 71B. For this reason, the light guide 71B does not have a surface corresponding to the light reflection surface 71d of the light guide 71 in FIG.

  Specifically, in the central region 71g of the light guide 71B, the width of the light guide 71B, the width of the light emitting surface 71a, and the width of the emitted light amount adjusting unit 71e in the direction orthogonal to the longitudinal direction Q of the light guide 71B. F is constant, and on both sides of the central region 71g, the width of the light guide 71B, the width of the light emission surface 71a, and the width F of the emission light quantity adjustment unit 71e are close to the light incident surfaces 71b at both ends of the light guide 71B. It is getting narrower gradually.

  Further, as shown in FIG. 13B, the pitch, height, and width of each inclined surface 71f forming the sawtooth-shaped vertical section of the emitted light amount adjusting unit 71e (the inclined surface in the longitudinal direction Q of the light guide 71). The width of 71f is set constant.

  The emitted light quantity distribution of the light guide 71B is as shown in FIG. 13C, and the center of the light guide 71B is similar to the emitted light quantity distribution of the light guide 71 shown in FIG. 11C. The decrease in the amount of emitted light in the vicinity is reduced by Δs, and the amount of emitted light in the vicinity of the center is increased by Δs.

  For this reason, the deviation of the emitted light quantity distribution shown in FIG. 13C and the deviation of the transmitted light quantity distribution shown in FIG. 13D are canceled well, and the CCD 47 receives the light as shown in FIG. The received light amount distribution received on the surface is uniform.

  Further, as apparent from FIG. 13C, the emitted light quantity distribution changes smoothly and does not change so as to be stepped. Therefore, the peripheral light quantity caused by the cosine fourth law of the imaging lens 46 is reduced. It can compensate well.

  Next, third to tenth embodiments will be described. In the third embodiment, the light guide 71 shown in FIGS. 11 (a) and 11 (b) or the emitted light amount adjusting unit 71e and the two side surfaces 71i of the light guide 71B shown in FIGS. 13 (a) and 13 (b) are covered. Since it is disposed inside the fitting groove 62a (shown in FIG. 3) of the shape holding member 62, the inner wall of the fitting groove 62a is subjected to plating or white coating, or the inner wall of the fitting groove 62a is a white sheet. Or paste. As a result, the light leaking out of the light guide 71 or 71B from the emitted light amount adjusting unit 71e and the side surfaces 71f is reflected inside the fitting groove 62a and returned to the inside of the light guide 71 or 71B. The amount of light emitted from the light exit surface 71a can be increased.

  In the fourth embodiment, as shown in FIG. 12A, the width F of the emitted light amount adjusting unit 71e is made to coincide with the constant width of the light guide 71A, and then, for each inclined surface 71f of the emitted light amount adjusting unit 71e, By performing a partial surface treatment on the inclined surface 71f, the amount of reflected light of the inclined surface 71f is adjusted to set an emitted light amount distribution as shown in FIG. 11C or FIG. 13C. Examples of the partial surface treatment for the inclined surface 71f include white paint, black paint, and chemical treatment. The amount of reflected light can be increased by white coating, and the amount of reflected light can be decreased by black coating. Further, the light reflectance of the inclined surface 71f can be adjusted by chemical treatment.

  In the fifth embodiment, the emitted light amount adjusting unit 71e of the light guides 71 and 71B is not a saw blade-like vertical cross-sectional shape, but a wave-like vertical cross-sectional shape, a longitudinal section in which a large number of semicircles and semi-ellipses are continuously arranged. The surface shape.

  In the sixth embodiment, one side surface in the longitudinal direction Q of the light guide opposite to the light emitting surface 71a is formed on a flat surface, and a black or white stripe pattern is formed on the flat surface in the longitudinal direction Q of the light guide. Then, the width of the stripe pattern in the direction orthogonal to the longitudinal direction Q of the light guide is changed depending on the position in the longitudinal direction Q of the light guide to form the emitted light amount adjusting unit 71e. For example, in the case of a white stripe pattern, as the width of the stripe pattern becomes wider, the reflected light amount of the emitted light amount adjusting unit 71e increases, the emitted light amount from the light emitting surface 71a increases, and conversely, the width of the stripe pattern increases. As the beam becomes narrower, the amount of light reflected by the emitted light amount adjusting unit 71e decreases and the amount of emitted light from the light emitting surface 71a decreases, so that the emitted light amount distribution in the longitudinal direction Q of the light guide can be set as appropriate.

  In the seventh embodiment, the width of the emitted light amount adjusting unit 71e in the direction orthogonal to the longitudinal direction Q of the light guide is smoothly changed. In this case, as shown in FIGS. 11A and 12A, when the light guide is viewed in plan, both sides along the longitudinal direction Q of the emitted light quantity adjusting unit 71e draw a smooth straight line or curve. . Thereby, the emitted light quantity distribution in the longitudinal direction Q of the light guide can be changed more smoothly.

  In the eighth embodiment, the width F of the emitted light amount adjusting unit 71e of the light guide 71 is not gradually reduced as it approaches the light incident surfaces 71b at both ends of the light guide 71, but the width of the emitted light amount adjusting unit 71e. Change and set F in various ways. For example, the width F of the emitted light amount adjusting unit 71e is widened near both ends and the center of the light guide 71 and narrowed at other portions. Thereby, the emitted light quantity distribution in the longitudinal direction Q of the light guide can be variously set.

  In the ninth embodiment, the cross-sectional shape of the light guide 71 or 71B is not rectangular, but is set to another cross-sectional shape. For example, the cross-sectional shape is circular or elliptical.

  In the tenth embodiment, the number of LEDs 72 is increased instead of disposing one LED 72 at each end of the light guide 71 or 71B. Thereby, the emitted light quantity from the light-projection surface 71a can be increased. The first to tenth embodiments may be appropriately combined.

  As mentioned above, although preferred embodiment and modification of this invention were described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image reading apparatus 3 Document conveying apparatus 4 Printing part 5 Paper feed cassette 11 Optical scanning apparatus 12 Developing apparatus 13 Photosensitive drum 14 Drum cleaning apparatus 15 Charger 17 Fixing apparatus 21 Intermediate transfer belt 26 Secondary transfer apparatus 43 Scanning unit 45 Illumination device 46 Imaging lens 47 CCD (reading unit)
51-54 1st-4th reflective mirror 61 Case 62 Cover-like holding member 63 CCD board 64 LED board 65 Heat sink 71 Light guide 71a Light emission surface 71b Light incident surface 71d Light reflection surface 71e Emission light quantity adjustment part 72 LED (light source)

Claims (4)

A long main body having translucency, a light incident surface formed at an end in the longitudinal direction of the main body, a light emitting surface formed on a side surface along the longitudinal direction of the main body, and a longitudinal direction of the main body Is formed on the other side surface along the light-emitting surface, and has an emitted light amount adjusting unit facing the light emitting surface, and guides light incident on the light incident surface inside the main body and reflects it by the emitted light amount adjusting unit. A light guide that exits from the light exit surface,
The emission light amount adjusting unit has a width in a direction orthogonal to the longitudinal direction, which varies depending on the position in the longitudinal direction, and is constant in a central region in the longitudinal direction, and in the longitudinal direction in both side regions of the central region . It is configured to gradually narrow as it approaches the end,
In the direction orthogonal to the longitudinal direction, the width of the light emitting surface and the width of the emitted light amount adjusting unit coincide with the width of the main body. A light guide according to claim 1;
An illumination device comprising: a light source that emits light to the light incident surface of the light guide. A lighting device according to claim 2;
An image reading apparatus comprising: a reading unit that reads an irradiated object illuminated by light emitted from the light emitting surface of the light guide of the illumination device. An image reading device according to claim 3,
An image forming apparatus comprising: a printing unit configured to print an image of the irradiated object read by the image reading device on a recording sheet.

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